A filter device is known from DE 10 2014 000 490 A1 and has a filter housing defining a main axis, in which at least one filter element is replaceably accommodated, and which has a housing pot surrounding the particular filter element. A housing head is removably attachable to the housing pot, has at least one fluid passage for the discharge flow of filtrate formed in it, and has a valve device associated with the fluid passage. The valve device includes a closing body that, in a closed position, blocks the discharge flow of filtrate and, in a release position, allows the discharge flow. A locking device includes a blocking element that, in a locking position, locks the closing body of the valve device in the closed position. The blocking element may be moved out of the locking position into an inoperative unlocking position by a control element provided on the particular filter element that, when the filter element is situated in the functional position in the housing pot, mechanically acts on the blocking element as the housing head is being attached to the housing pot.
Because in the known solution, the blocking element of the locking device is mounted in the housing pot for axial displacement along the main axis for its movement between the locking position and unlocking position and, when attaching the housing head, can be moved into the unlocking position through contact with the control element of the filter element, the blocking element may be moved by the control element of the filter element directly into the unlocking position during the relative axial movement taking place as the housing head is attached to the housing pot. In general, when actuating the known device with low actuation forces, a low material load also then occurs, which permits the use of cost-efficient materials, such as synthetic materials, for the relevant functional elements in the known solution.
When the housing head is attached to the housing pot in the known solution with no filter element situated in the functional position, a valve plate of the valve device remains locked in its closed position. The associated discharge flow valve then remains closed. In this case, a faulty initial operation with no filter element is ruled out as is the insertion of a non-fitting filter element, which may also constitute a type of inexpensive knock-off.